Input: smtpe-ts - use msecs_to_jiffies() instead of HZ

Use msecs_to_jiffies(20) instead of plain (HZ / 50), as the former is much
more explicit about it's behavior. We want to schedule the task 20 mS from
now, so make it explicit in the code.

Signed-off-by: Marek Vasut <marex@denx.de>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>